In a screening inspection of a power semiconductor device including a power semiconductor element such as a power metal oxide semiconductor field-effect transistor (MOSFET) or an insulated-gate bipolar transistor (IGBT), a screening voltage is applied to a gate terminal of the power semiconductor element to inspect an electrical isolation of a gate oxide film of the power semiconductor element. The screening voltage is set greater than a gate breakdown voltage rating of the power semiconductor element.
As disclosed, for example, in JP-A-H5-67661, U.S. Pat. No. 5,502,399 corresponding to JP-A-H7-142711, or U.S. Pat. No. 5,828,081 corresponding to JP-A-H7-283370, a power semiconductor device has been proposed that has a terminal for receiving an inspection signal and switches to an inspection mode in response to the inspection signal. Thus, a screening inspection can be conducted effectively.
As disclosed, for example, in U.S. Pat. No. 6,218,889 corresponding to JP-A-H11-177087, a power semiconductor device has been proposed that has a protection circuit constructed with a zener diode to protect a power semiconductor element from static electricity damage.
In the power semiconductor device disclosed in U.S. Pat. No. 6,218,889, an inspection of the protection circuit must be conducted in addition to a screening inspection of a power semiconductor element. If a protection voltage (i.e., zener voltage) of the protection circuit is set greater than a screening voltage, a voltage greater than the screening voltage is applied to a gate electrode of the power semiconductor element during the inspection of the protection circuit. As a result of the inspection of the protection circuit, the gate electrode of the power semiconductor element deteriorates. The power semiconductor devices disclosed in JP-A-H5-67661, U.S. Pat. Nos. 5,502,399, and 5,828,081 are not directed to reduce the deterioration resulting from the inspection of the protection circuit.